I have a bike that did not come with gears. It is a rear hub driven ebike with a single speed. Eventually when the warranty runs out, I want to put gears in it and turn it to a mid drive. Now I know that the reasonable thing to do is to just get a bike with gears and put a mid drive in it but I really like the frame, accessories, and mounts it has. Also I am passionate about tinkering and sometimes passion and reason do not really mix.

I have looked at and studied the area I am going to be working on the bike. It has a vertical dropout and the distance between the two inner dropouts is 135mm.

Reading Sheldon Brown's site, it says I can fit a 7, 8, or 9 speed cassette. I had a spare 9 speed Wheelset from a gravel Bike and I let it sit between the dropouts and I verified it fits with disc brakes.

However, the next and hardest piece of the puzzle is finding a derailleur hanger. I know that hangers are specific to each bike, but I'm kind of hoping that there could be one that could work. After browsing through hundreds of hangers out there, I can't seem to find one that may fit the drive side drop out. One thing I noticed though is that dropouts with hangers usually have a notch where the hanger would sit to keep it from moving. My drop out doesn't have that notch.. The only thing that would keep the derailleur from moving would be a small hole for a 4mm hex bolt which is primarily used to hold one side of the rear fender and the axle skewer itself.

If I were to get a derailleur hanger for this frame that may work, I would need to drill a hole in the drive side dropout. This would compromise the integrity of the dropout/ frame which I don't like but is the only way I can see myself bolting a derailleur hanger.

My other option to add gears would be to just get an internal gear hub such as a Shimano Alfine. No drilling or crazy mods involved so the frame would keep its integrity. But I really prefer the derailleur setup over the IGH.. it reminds me of when I was a kid with my first mountain bike..

So my questions are:

Is there something I can bolt on to the rear drop out so I can attach a derailleur hanger? I don't care if it looks weird as long as I can get a derailleur hanger on there

If there is no such part, would drilling a hole to accomodate a derailleur hanger be a viable? Would frame integrity really be compromised that much?

enter image description here

  • 1
    A photo would help a lot. Is your dropout actually made for a derailleur hanger? Maybe the screw hole is intended for a mudguard or rear rack? Does a similar one exist on the left side? Maybe an emergency derailleur hanger would work.
    – Michael
    Nov 16, 2022 at 10:08
  • Hi. Sorry the image did not upload.. I am new to this site. Here is a pic [IMG]imgur.com/a/k1JlFuN[/IMG]
    – badcircle
    Nov 16, 2022 at 16:44
  • Cropped, downsized, and added the image. The simplest approach is just to make sure it's within the 2mb size limit and paste it in directly. Nov 16, 2022 at 18:13
  • To me it looks like there’s a good chance that the weird almost vertical chainstay would interfere with a derailleur.
    – ojs
    Nov 17, 2022 at 1:00

3 Answers 3


There is a way of doing this: a rotary file and confidence. Here are some images lifted from Yellow Jersey's site.

enter image description here enter image description here enter image description here

Since you have less of a slab of dropout to work with, you'd probably do it by using a surrogate replaceable hanger that uses M3 fixing screws rather than a big hole for a sleeve nut.

The tool you would use is something like this:

enter image description here

You would want to have some way of controlling or at least easily visualizing the depth of the cut to create a flat surface.

You could also do it by just using a Wheels Mfg emergency hanger forever. I hate everything about that idea but it could produce a bike that goes.

IGH is a way better idea. However, converting to an RD via the above surgery with sufficient planning and control is probably achievable.

  • That's a ballsy fix - would a bolt-on generic claw hanger work? Probably find the dropouts are too short and the axle would end up under the slots.
    – Criggie
    Nov 16, 2022 at 22:49
  • 1
    @Criggie You could maybe contrive a way of making a generic claw hanger work, but they're made with a nub intended to fit into a horizontal dropout, so you'd have to modify it a bunch just to wind up with it able to float awkwardly on top. At that point it's kind of the same proposition as just using the Wheels emergency hanger. Nov 16, 2022 at 23:48
  • Would another option be to fabricate a hanger that fits the vertical dropout and uses the fender bolt for securing it with wheel removed? Possibly more complex task, but saves frame surgery
    – mattnz
    Nov 17, 2022 at 2:34
  • @mattnz Yes I can see that, but the sky is the limit here if fabricating something complex is on the table. Nov 17, 2022 at 3:10
  • Ballsy indeed. I guess if you've already written the frame off, there's nothing to lose.
    – Adam Rice
    Nov 17, 2022 at 18:28

Without seeing what you've got, I doubt very much that you could drill a hole in your existing dropout to create a derailleur hanger--there's just not enough metal there. Derailleurs take 10-mm bolts. That's a pretty big hole.

In the old days—say, up until roughly 1980—bikes often were built without derailleur hangers, and the derailleur was bolted to a clip-on hanger like this

Old simplex derailleur

Your axle would fit into that hook opening, which did the work of holding the derailleur in place; that extra screw you see on the hanger would fit into a small hole behind the dropout to retain the derailleur, but would be insufficient to hold it in operation.

But there would be a couple of problems attempting to use this in your case:

  • These were always designed to be used with horizontal dropouts, so I doubt you could get the right orientation.
  • These were used with imprecise, non-indexed 5- or 6-speed drivetrains. Getting an indexed 9-speed drivetrain to work with this would be very difficult.

There have been a handful of exotic derailleurs--and some very old derailleurs--that clamped to the chainstay roughly at its midpoint, but good luck finding these.

The alternative is to cut out your current dropout and weld/braze/bond in a new one with a derailleur hanger. I hope it's obvious that this would be a major undertaking.

All in all, I think this is a bad idea.

  • 1
    This is called claw mount and lowest tier derailleur are still made like this. Note the bolt next to the notch: It's used to fix the derailleur to the frame because otherwise you'd need more than two hands to get the wheel and derailleur into right positions.
    – ojs
    Nov 16, 2022 at 15:46
  • Thank you. Yes I had a feeling I should not drill a hole.. I looked into that claw mount before posting my question and it seems I will not be able to mount it correctly with my vertical dropout. Too bad they don't make one for vertical drop outs.. Regarding the mid mounted derailleur, am I able to mount those where my chain tensioner is? [IMG]imgur.com/a/k1JlFuN[/IMG]
    – badcircle
    Nov 16, 2022 at 16:46
  • Probably not. And I should point out that the newest mid-mounted derailleur was made 30 years ago, and was uncommon even then.
    – Adam Rice
    Nov 16, 2022 at 18:10
  • 1
    @badcircle you will need to fabricate something like the claw mount that will work on your dropout. It will take some skill and planning but it can be done.
    – David D
    Nov 16, 2022 at 19:01

Thank you for the answers everyone. I appreciate it. It just cemented the fact that getting a derailleur hanger into the drop out would be a huge undertaking versus just getting an IGH. I do still want to look into the derailleur a bit more. I took more measurements tonight and did some searching which is why it took a while to reply.

First I would need to find a derailleur hanger that uses small screws and would fit in the tiny area of the dropout. If you see the image below, there really isn't much room in that drop out:





I took a measurement of the thickness of the dropout as well if I were to file and file a notch.


Here are some hangers I found with small screws that look like may fit:



Based on everyone’s answers and my thoughts I listed down some options:

Option A: Hardest to Execute/ Non reversible/ $$ Find a suitable hanger and file notch into dropout

I want to remove as little material as possible.

It looks like the dropout is about 8mm thick based on the photo above. If I were to file this down so it is 6mm thick, would it be too little?

Option B: Medium Difficulty/ Non reversible/ $$ Find a suitable hanger and drill holes for the new screws

Smaller screws mean less material removed.

If I tap and drill slow are the chances of forming a crack in the aluminum really that high?

Option C: Easy to execute/ Reversible/ $$ Find a suitable hanger and clamp it down with mini c clamps.

I used c clamps like these (https://www.amazon.ca/BOOHAO-Stainless-Openings-Carpentry-Woodwork/dp/B0991R4NSC/ref=sr_1_3_sspa?crid=10ZSB2VPGK0MR&keywords=mini+c+clamps&qid=1668671879&qu=eyJxc2MiOiIzLjIzIiwicXNhIjoiMi44OCIsInFzcCI6IjIuMjMifQ%3D%3D&sprefix=mini+c+clamps%2Caps%2C129&sr=8-3-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1 ) when I retrofitted HIDs into my car’s headlights years ago. They are strong enough to hold the housing to the body of the headlight assembly. Assuming I can find the right lengths of clamps, I think the derailleur hanger could attach securely while it hangs on the skewer and two clamps. No drilling or filing required.

Option D: Easy to execute/ Reversible/ $ Buy emergency hanger and install

My only concern is that I read that not all gears work?

Option E: Hard to execute/ Reversible/ $$$$ Custom Fabricate Derailleur Hanger

There is a washer that sits between the dropout and the fender mounting stick. I took off that washer and traced it on a piece of paper with measurements. It might be a silly idea but I thought I could use this as a base to 3D Print my own derailleur hanger. The hanger would be held by the skewer and the one bolt that bolts the fender down. I think it would be similar to the “claw” hangers for horizontal mount.




Option F: $$$/ Reversible/ $$$$$ Just get an IGH

Pretty self explanatory lol.

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